During a Christmas gathering at Conan O’Brien’s Los Angeles home, a dramatic altercation unfolded between Rob Reiner and his son Nick. The holiday celebration took a tense turn when the 32-year-old Nick engaged in a heated argument with his parents, Rob, 78, and Michele, 70, leaving other guests in shock.

Witnesses at the party described Nick’s behavior as erratic throughout the evening. The situation escalated to such an extent that one guest considered calling 911 to diffuse the conflict. However, sources revealed to the Daily Mail that Conan O’Brien intervened, urging his friend not to involve the authorities.

“The argument between the father and son became extremely loud and intense,” an insider explained. “It got to a point where someone thought it was necessary to call the police.”

O’Brien reportedly took control, saying, “It’s my house, my party, I’m not calling the police,” convincing the concerned guest to refrain from making the call. Despite the chaos, the celebrated host has not provided any comment on the incident.

‘But Conan stepped in and said, “it’s my house, my party, I’m not calling the police.” He talked them out of calling the police.’

O’Brien, 62, did not respond to the Daily Mail’s requests for comment. 

Another source corroborated the account, saying party guests had raised concerns about Nick’s mental state and suggested contacting the cops before O’Brien shut the idea down. 

‘When the s**t was hitting the fan, somebody said we need to call the police. The conversation was about getting this kid put into a mental-health hold,’ the second source told the Daily Mail. 

Conan O’Brien stopped a friend from calling 911 during an explosive fight between Rob and Nick Reiner at the comedian’s Christmas party 

Multiple attendees have reported witnessing Rob, 78, and wife Michele, 70, having a heated argument with 32-year-old Nick at O’Brien’s Los Angeles mansion (pictured) on Saturday night

One source familiar with the party said the spat grew so intense that at least one guest suggested calling the cops to intervene 

‘Conan O’Brien stepped in and said, “no, I don’t want the police at my house”. It makes sense; who wants the cops showing up creating a scene?’ the insider added.

‘But the argument between Rob and Nick was pretty intense.’

A source close to the Los Angeles Police Department said there were no 911 calls from O’Brien’s house on Saturday night.

And despite partygoers’ concerns, nobody predicted what would happen next: that Rob and Michele Reiner would be found dead from knife wounds less than 24 hours later.

‘Only the murderer is responsible,’ the first source said. 

‘But it must be gut-wrenching for Conan to learn that this is how things turned out. I’m sure that night is replaying for him over and over.

‘It’s just so awful and sad.’

In another haunting revelation, the Daily Mail has also learned that Rob Reiner had confided to friends at the O’Brien party about being scared of his own son. 

The beloved filmmaker, 78, and his wife Michele Reiner, 70, were found dead at their Brentwood home on Sunday December 14

‘They got in an argument, the father and son. It got so bad and loud someone wanted to call the police to report it,’ one insider claimed. (Pictured: Albert Brooks, O’Brien and Reiner in 2024)

‘I’m petrified of him. I can’t believe I’m going to say this but I’m afraid of my son. I think my own son can hurt me,’ Reiner allegedly said immediately after his altercation with Nick.

Those comments resurfaced at an impromptu memorial attended by Hollywood A-listers on Monday, where the details of the party were discussed, according to a source.

The insider told the Daily Mail that several attendees were left in tears upon hearing what Rob had said.

The Daily Mail contacted representatives for all the stars in attendance at Monday’s impromptu memorial. One spokesman denied that Rob had made the comments about Nick at O’Brien’s party.

TMZ first reported that Reiner had had a ‘very loud argument’ with his son at the holiday party, after which the legendary movie director and his wife left.

The Reiners had reportedly brought Nick – who has a history of substance abuse and instability – to the star-studded event to ‘keep an eye on him.’ 

Nick had been living in the guesthouse of the Reiners’ own Brentwood mansion, after years of substance abuse issues, at least 18 stints in rehab and some periods of homelessness.

Insiders also revealed he was suffering with worsening schizophrenia and became ‘erratic and dangerous’ when doctors changed his medication weeks before the tragedy. 

But guests at the A-list packed party say Nick displayed ‘antisocial behavior’, such as staring at attendees and ‘kept asking people if they were famous,’ according to reports.  

Nick was in court Wednesday wearing a blue anti-suicide vest, it was his first appearance since the death of his parents. He has been charged with two counts of first-degree murder

One source told NBC News that at one point Nick ‘interrupted’ comedian Bill Hader, who then told Reiner’s son that he was ‘in the middle of a private conversation’ – prompting an angry outburst. 

‘Nick just stood there and stared before storming off,’ the witness said. 

Hours later, Rob and Michele Reiner were found dead at their home, with Nick charged with their murders. 

The couple was discovered by their youngest daughter Romy, 27, who lived across the street from her parents’ Brentwood property.

The two were found in bed with their throats cut and may have been asleep when they were murdered, a source close to the investigation claimed to the Daily Mail.

Nick, who lived in his parents’ guest house, was arrested several hours later 15 miles away from their Brentwood house. 

He had earlier checked in to The Pierside Santa Monica, where staff reportedly later discovered a shower ‘full of blood’ and a trail leading off of his bed, as well as a window covered up by bedsheets.

Nick, who is known to have a history of drug addiction and volatile mental health, is now facing federal murder charges and is being held without bail. 

Investigators have not yet offered any potential motive for the murders. 

Nick’s first court hearing was set for Tuesday morning at the Clara Shortridge Foltz Criminal Justice Center, but was delayed because he was not medically cleared to be transferred from the jail to the courthouse, according to his attorney Alan Jackson.